The Eurasian Treecreeper is a woodland specialist most often found climbing up the trunks of trees from where it picks its food. It is a well camouflaged bird, and can be a bit difficult to spot if you aren't used to them, but once you are used to it it often seems like they can turn up on any tree anywhere. As they are often in the thick of branches they can be a bit tricky to photograph, but persevere and you'll almost certainly eventually encounter a more approachable one. In colder months, look near tit flocks, which they sometimes seem to accompany.